As the nation's first African-American president, Obama's racial identity has remained front-and-center through the first 4½ years of his presidency. He's spoken of his own improbable story as evidence of how far the nation has come, even as he's battled with detractors who have spoken of his "otherness" as a handicap to leading the nation.

When the president steps to the dais at the Lincoln Memorial on Wednesday to deliver remarks marking the 50th anniversary of the March on Washington, he will undoubtedly note that his own rise connects directly to the blood, tears and work of Martin Luther King and his civil rights contemporaries.

Over the years, his most compelling remarks on race stretch from reflections as a young man grappling with his identity to his thoughts last month after a Florida jury acquitted George Zimmerman in the shooting death of African-American teenager Trayvon Martin.

Some of these comments have been lauded by his supporters as thoughtful and heartfelt, while others have derided them as divisive rhetoric that stoke the nation's continued racial divide.

July 1995, Dreams from My Father: A Story of Race and Inheritance.

Before launching his political career, Obama penned a book delving into his own journey as the son of a black African father and white American mother:

"The emotions between the races could never be pure; even love was tarnished by the desire to find in the other some element that was missing in ourselves. Whether we sought out our demons or salvation, the other race would always remain just that: menacing, alien, and apart."

March 5, 2007, Selma, Ala.

The then long-shot presidential candidate Sen. Barack Obama spoke from the pulpit of the historic Brown Chapel A.M.E. Church of his own claim to a place in the civil rights movement:

"I'm here because somebody marched. I'm here because you all sacrificed for me. I stand on the shoulders of giants. I thank the Moses generation; but we've got to remember, now, that Joshua still had a job to do. "

March 18, 2008, Philadelphia.

After video of Obama's former pastor, Jeremiah Wright, making a series of racially controversial statements surfaced in the heat of the presidential race, Obama spoke about race in the USA:

"I can no more disown him than I can disown the black community. I can no more disown him than I can my white grandmother - a woman who helped raise me, a woman who sacrificed again and again for me, a woman who loves me as much as she loves anything in this world, but a woman who once confessed her fear of black men who passed by her on the street, and who on more than one occasion has uttered racial or ethnic stereotypes that made me cringe.

"These people are a part of me. And they are a part of America, this country that I love."

July 22, 2009, news conference.

About six months into his first term, Obama was asked during a prime-time news conference about the arrest of Henry Louis Gates, a noted African-American scholar who was arrested outside his own home:

"I don't know, not having been there and not seeing all the facts, what role race played in that (Gates case). But I think it's fair to say, number one, any of us would be pretty angry; number two, that the Cambridge police acted stupidly in arresting somebody when there was already proof that they were in their own home; and, number three, what I think we know separate and apart from this incident is that there's a long history in this country of African Americans and Latinos being stopped by law enforcement disproportionately. That's just a fact."

March 23, 2012, Washington.

President Obama weighed in on the shooting death of unarmed black teenager Trayvon Martin for the first time more than a month after the killing had spurred a national uproar:

"My main message is to the parents of Trayvon Martin. You know, if I had a son, he'd look like Trayvon. All of us as Americans are going to take this with the seriousness it deserves."May 19, 2013, at Morehouse College, Atlanta.

Obama delivered the commencement address at Morehouse, the country's pre-eminent historically black college and the alma mater of King:

"Just as Morehouse has taught you to expect more of yourselves, inspire those who look up to you to expect more of themselves. We know that too many young men in our community continue to make bad choices. And I have to say, growing up, I made quite a few myself. Sometimes I wrote off my own failings as just another example of the world trying to keep a black man down. I had a tendency sometimes to make excuses for me not doing the right thing. But one of the things that all of you have learned over the last four years is there's no longer any room for excuses."

July 19, 2013, Washington.

After George Zimmerman was found not guilty in the shooting death of Trayvon Martin, Obama tried to explain African Americans' response:

"When Trayvon Martin was first shot, I said that this could have been my son. Another way of saying that is Trayvon Martin could have been me 35 years ago. ... When you think about why, in the African-American community at least, there's a lot of pain. It's important to recognize that the African-American community is looking at this issue through a set of experiences and history that doesn't go away."